This invention relates to mounting a combination engine/transmission in a front wheel drive vehicle and more particularly to supporting a transversely mounted engine/transmission with an arrangement to counter rotation of the engine/transmission in it mounts.
In recent times, there has been a major effort to increase fuel economy of automotive vehicles and there have been several technical trends developed to achieve increased fuel economy. One such trend is an increase in front-wheel-drive vehicles where the weight of the engine is placed over the traction wheels of the vehicle. Another trend to increase fuel economy is to provide smaller V-6 or straight line four-cylinder engines instead of the previously utilized V-8 engine. Still another trend is to make the vehicle smaller and lighter-weight. The comfort of the vehicle""s occupants is very important in the effort to encourage car buyers to consider smaller and lighter vehicles. It is clear to those skilled in the art of vehicle engineering design that a major factor for maximizing occupant comfort is to minimize vibrations and noise, particularly those associated with the engine and transmission.
In front-wheel-drive vehicles, it is common engine and transmission mount practice to design the mounts to handle a torque reaction of the powertrain as well as supporting the assembly. The torque reaction comes from the action of the engine/transmission in the mounting arrangement and from the action of the entire powertrain at the differential or at the torque output to the driving wheels. It has been common practice to design the mounts to handle the torque reaction of both the engine/transmission and the differential (or powertrain output). Where the engine/transmission are mounted longitudinally in the vehicle (as opposed to being mounted transversely), the engine/transmission""s torque reaction is in the vehicle""s overall roll direction as defined as a moment about a generally longitudinal axis relative to the vehicle. On the other hand, the differential related torque reaction is in the vehicle""s pitch direction as defined as a moment about a generally lateral axis relative to the vehicle. As a result, the two torque reaction effects are not additive and thus it is not difficult for the engine/transmission mounts to handle both torque reactions utilizing the spring rate of the engine/transmission cushion mounts.
When an engine/transmission of a vehicle is mounted transversely, the torque reaction of the engine/transmission is in the vehicle""s pitch direction (moment about a laterally extending axis). The torque reaction of the differential is also in the vehicle""s pitch direction. Thus, both torque reactions are additive and are directly coupled together acting upon the engine mounting arrangement. This effect imposes a very significant burden on the mounting arrangement since the resultant cumulative loads in the pitch direction includes both the engine/transmission""s normal torque reaction and the differential""s torque reaction which is effected by the effective transmission ratio and the axle ratio.
According to conventional practice and irrespective of the relative position of the engine and transmission in the vehicle, it is desirable for deriving a maximum benefit in isolating the vibration of the sprung mass including the powertrain and differential that the engine/transmission mounts be located adjacent to the points of minimum vibratory force in the powertrain system, i.e. node points. However, where a compact vehicle utilizes a transversely mounted engine of the type exhibiting relatively great vibration characteristics, e.g. an in-line four-cylinder, typically there is very little space available for conventional cushion mounting arrangements sized to effectively control pronounced powertrain vibrations as well as vertical motion or shake and any pitching motion.
The concerns identified above have been previously addressed and the combination engine/transmission mounting system disclosed in U.S. Pat. No. 4,901,814 to VonBroock, et al is known. VonBroock provides two engine mounts supporting an engine/transmission along three axes. The engine/transmission""s torque reaction is resisted by two torque struts. In a preferred embodiment, one of the engine mounts is close to the center of gravity of the engine/transmission combination. A second engine mount is placed near an end of the engine of the engine/transmission combination. A support bracket in the form of a crescent shape extends in a fore and aft direction of the vehicle within the engine compartment. The bracket is positioned near the center of gravity of the engine/transmission combination. As explained in VanBroock, the torque struts are positioned close to the center of gravity of the engine/transmission combination.
The VanBroock engine/transmission mounting arrangement has several disadvantages. The first disadvantage is the need for a support bracket to be installed within the engine compartment where room is sparse. This is very undesirable especially in small compact vehicles. Secondly, the addition of the support bracket requires that the vehicle fire wall which separates the engine compartment from the passenger compartment be reinforced to allow for attachment of the support bracket. Thirdly, the support bracket transmits vibrations of the engine/transmission to the passenger compartment in close proximity to the steering column of the vehicle. This is highly disadvantageous since this causes the vibrations to be amplified to the hands of the vehicle driver.
It is desirable to provide a mounting arrangement for an engine/transmission combination suitable for a front-wheel-drive vehicle and which minimizes the generation of undesired vibration. It is desirable to provide an engine/transmission combination mounting arrangement which is simple and inexpensive.
The present invention concerns a combination engine and transmission mounting arrangement suitable for a vehicle with front wheel drive and a transversely mounted engine. The mounting arrangement provides a first bearing support which translationally and fixably supports the weight of a first end portion of the engine/transmission combination. A second bearing support is provided for translationally and fixably supporting an opposite second end portion of the engine/transmission combination. A first torque strut is provided having a first end connected to a vehicle structural member adjacent to a rear corner of the engine compartment. The opposite second end of the torque strut is connected to the engine/transmission combination generally adjacent the first end of the portion of the engine/transmission combination. A second torque strut is provided which is in vertical alignment with the first torque strut. The second torque strut has a first end connected to a structural member of the vehicle adjacent the rear corner of the engine compartment. A second end of the second torque strut is connected to the engine/transmission combination adjacent to but lower than where the first torque strut""s second end attaches to the engine/transmission.
It is an object of the present invention to provide a combination engine/transmission mounting arrangement for an engine in a front-wheel drive and transverse mount vehicle.
It is another object of the present invention to provide a combination engine/transmission mounting arrangement for an engine in a front-wheel drive and transverse mount vehicle which minimizes powertrain vibrations.
The above noted and other objects of the present invention will become apparent to those skilled in the art from a review of the invention as it is provided in the accompanying drawings and detailed description of the preferred embodiment.